The relation between the solar wind input to the magnetosphere, vBSouth, and the auroral geomagnetic index AL is modeled with two linear moving-average filtering methods: linear prediction filters and a driven harmonic oscillator in the form of an electric circuit. Although the response of the three-parameter oscillator is ''simpler'' than the filter's, the methods yield similar linear timescales and values of the prediction-observation correlation and the prediction &khgr;2. Further the filter responses obtained by the two methods are similar in their long-term features. In these aspects the circuit model is equivalent to linear prediction filtering. This poses the question of uniqueness and proper interpretation of detailed features of the filters such as response peaks. Finally, the variation of timescales and filter responses with the AL activity level is discussed. ¿ American Geophysical Union 1995